1. Field of the Invention
The disclosure generally relates to the recovery of a vessel by a larger vessel in water. More specifically, the disclosure relates to the recovery of a vessel from a larger offshore vessel, such as an offshore platform or ship.
2. Description of the Related Art
Larger vessels in water, such as offshore platforms, FPSOs, and ships, often deploy and retrieve smaller vessels for reconnaissance, transport, and maintenance, and when needed, evacuation. Often, the smaller vessels can be unmanned, other than when used for evacuation. Typically, the smaller vessels are launched by being lowered using hoists and rope to the surface of the water and released, and then later retrieved by the same manner.
The launch of the smaller vessel from the larger vessel can be somewhat straightforward. The smaller vessel can be deployed generally by being suspended from the larger vessel by ropes or cables attached to the bow and stem of the smaller vessel, and the ropes or cables are released after the smaller vessel is lowered and floating on the water. The retrieval can be more complicated. An operator can maneuver the smaller vessel into position to be retrieved by the system that released the vessel into the water. However, the different heave motion of the larger vessel compared to the smaller vessel can cause difficulties in reattaching the ropes or cables to hoist the smaller vessel up to a storage position with the larger vessel.
One system shown in GB Pat. No. 2,150,903 and entitled, “Method and Assembly for Launching or Retrieving a Lifeboat,” describes in the Abstract: an assembly for launching or retrieving a lifeboat, pick-up boat or the like from a ship or a stationary installation includes a boat dock having float bodies. Control wires extending down to the sea from the ship or the stationary installation cooperate with guide means on the boat dock to control the dock during lowering and hoisting. In this manner, the boat dock can float in the sea and follow the wave movements, while at the same time being stabilized due to the control of the wires. There is a coupling means on the boat dock, which engages with a coupling means on the boat when the boat is in the dock. The system shows a boat with a ball on the end of a smaller diameter rod located on top of the boat that engages and disengages the coupling means (sized to fit the ball with the rod so that the ball does not slip through the coupling means) for launch and retrieval from the larger structure. For launch, the suspended dock with the boat is lowered to the water and the ball with the rod on the boat is released. For retrieval, the boat can approach the dock and as the boat passes under the dock horizontal bar, the ball and rod on the top of the boat can engage the horizontal bar to couple the boat with the dock, so that the dock and boat can be raised to a storage position. Variations of this system include lowering the boat on a separate line from the dock. However, the concentrated load from the tensile stresses with the ball and rod of the boat structure generally would require extra structural support that adds weight and may interfere with other desirable design features in the boat.
However, these systems generally depend on the maneuverability of the smaller vessel to approach a docking system in a controlled manner for retrieval. If maneuverability of the smaller vessel is lost, the retrieval of the vessel is compromised.
U.S. Pat. No. 8,578,872 discloses a life vessel retrieval system. The Abstract states: “A system for retrieving a life vessel from water and drawing the life vessel onto a deck of a rescue vessel comprises a life vessel system comprising: i) a tow-line comprising a first end portion secured to the life vessel and an opposed second end portion; and ii) a deployment system configured to deploy the second end portion of the tow-line into the water. The system further comprises a rescue vessel system comprising i) a towing device on the rescue vessel, the towing device configured to receive the second end portion of the tow-line and retract the tow-line to draw the life vessel towards the rescue vessel; and ii) a retrieval assembly assembled to the deck of the rescue vessel, the retrieval assembly configured to receive the life vessel as the life vessel is drawn towards the rescue vessel and to lift the rescue vessel onto the deck.” The life vessel has a tow-line secured on one end to a forefoot of a keel and a drogue mounted to the other end to orient the vessel in the water. The rescue vessel includes a towing device configured to receive the second end of the tow-line and retract the tow-line to draw the life vessel toward the rescue vessel and then slide from the water along a rail onto the deck of the rescue vessel.
There remains then a need to provide an improved system and method for recovery of a vessel, such as when control of the vessel has been compromised and customary methods of retrieval are inadequate.